[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT43 KNHC 302040
TCDAT3

Hurricane Franklin Discussion Number  41
NWS National Hurricane Center Miami FL       AL082023
500 PM AST Wed Aug 30 2023

The cloud pattern of Franklin has become oblong this afternoon,
likely due to increasing westerly shear associated with Idalia's
upper-level outflow. A ring of cold infrared cloud tops still
surrounds the large eye of the hurricane, which is now somewhat
elliptical in shape. The initial intensity is held at 90 kt, which
is supported by a T5.0 Dvorak classification from TAFB and UW-CIMSS
objective estimates between 85-90 kt. Radar images from Bermuda show
an outer rain band is spreading over the island, which will likely
result in gusty winds while it passes over the region.

Franklin is moving northeastward (55/11 kt) between a deep-layer
trough over the northeastern United States and a high pressure ridge
over the central Atlantic. The track guidance remains in good
agreement on the hurricane moving generally east-northeastward and
away from Bermuda during the next couple of days, and little change
was necessary to this part of the forecast. There are still
along-track differences in the global models regarding Franklin's
track at days 3-5 related to its interaction with the upper trough.
But, there is at least general agreement that the cyclone will turn
northeastward after it merges with a frontal system over the
northern Atlantic. The updated NHC track forecast remains relatively
close to the HFIP corrected consensus approach (HCCA) aid during
this period.

The satellite structure of Franklin is gradually degrading, and the
increasing shear that is forecast should keep the hurricane on a
weakening trend. The updated intensity forecast is fairly similar to
the previous one, with the most notable change being that Franklin
is now forecast to become a powerful extratropical cyclone by 72 h.
Some of the global guidance suggests this could occur even sooner,
so future forecast adjustments may be necessary. Although weakening
is forecast, the wind field is likely to grow in size as Franklin
moves deeper into the mid-latitudes.


KEY MESSAGES:

1. Tropical storm conditions, mainly in gusts, are expected on
Bermuda into this evening while Franklin passes north of the island.

2. Life-threatening surf and rip currents are occurring along the
east coast of the United States. These conditions are expected to
continue during the next day or two.


FORECAST POSITIONS AND MAX WINDS

INIT  30/2100Z 34.2N  65.9W   90 KT 105 MPH
 12H  31/0600Z 34.9N  63.9W   85 KT 100 MPH
 24H  31/1800Z 35.8N  60.8W   75 KT  85 MPH
 36H  01/0600Z 36.9N  57.4W   70 KT  80 MPH
 48H  01/1800Z 38.1N  53.9W   65 KT  75 MPH
 60H  02/0600Z 39.7N  50.7W   65 KT  75 MPH
 72H  02/1800Z 41.6N  47.5W   60 KT  70 MPH...POST-TROP/EXTRATROP
 96H  03/1800Z 45.0N  42.4W   45 KT  50 MPH...POST-TROP/EXTRATROP
120H  04/1800Z 50.0N  37.5W   40 KT  45 MPH...POST-TROP/EXTRATROP

$$
Forecaster Reinhart
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